SANTA ANA PUEBLO, N.M. – Only certain classes of antibiotics increased the risk of yeast infections in a study of 650 women followed for 18 months to see what factors were associated with new-onset vulvovaginal candidiasis.
Penicillins increased the risk the most (adjusted hazard ratio, 4.1), followed by cephalosporins (aHR, 3.3) and metronidazole (aHR, 2.8), compared with women who did not report antibiotic use. Other classes of antibiotics were not associated with yeast infections.
"Many women and physicians believe that if you take an antibiotic, you’re just bound to get yeast. The message is that not all antibiotics are associated with yeast vaginitis; it’s certain classes of antibiotics that carry the highest risk," said senior investigator Sharon L. Hillier, Ph.D., a professor of obstetrics and gynecology and reproductive sciences at the University of Pittsburgh.
"When women are given antibiotics, I think it’s useful to help them understand they have some likelihood of getting a yeast infection with these three, and less so with quinolones or tetracyclines or something else," she said at the annual scientific meeting of the Infectious Diseases Society for Obstetrics and Gynecology.
The 650 subjects – 18-40 years old, not pregnant, and with no signs or symptoms of yeast at baseline – were followed at 2-month intervals during the investigation, and had a total of 4,934 follow-up office visits. Each time, they were asked what antibiotics they had been on, if any, among other questions.
There were 82 clinical yeast vaginitis diagnoses and 58 self-diagnosed infections with documented antifungal use. The results were largely similar when the team limited analysis to just clinically diagnosed cases.
A total of 312 women used an antibiotic at least once. Macrolides, metronidazole, and penicillins were used most often among the nine classes of reported antibiotics. The most common indications were upper respiratory tract infections, bacterial vaginosis, urinary tract infections, and sexually transmitted infections.
Having two or more male sexual partners was also a strong predictor of yeast vaginitis (aHR, 5.0), "and that was something that was a little bit surprising because it’s not a sexually transmitted infection. It’s useful maybe to tell women that limiting their numbers of sex partners will also decrease their risk," Dr. Hillier said.
Using depot medroxyprogesterone acetate (Depo-Provera), meanwhile, had a protective effect (aHR, 0.3), compared with women not using hormonal contraceptives. "Depo-Provera has a very strong progestin; some women who get the shot actually have estrogen depletion in the vaginal epithelium. The finding suggests that when you remove the estrogen from the [vaginal] epithelium, it can reduce your risk for yeast vaginitis," Dr. Hillier said.
Other forms of hormonal contraception were not associated with yeast vaginitis. Although "many women believe oral contraceptives and other hormonal methods increase the risk, there was no evidence of increased risk in this study," she said.
Dr. Hillier said she had no disclosures. The work was funded by the National Institutes of Health.